B1690 — Autolamp Delay Circuit Open

The trouble code B1690 indicates a problem within the vehicle’s autolamp delay circuit, which is responsible for controlling the automatic headlamp functions, including delay features. In simple terms, this code suggests that the control circuit for the delayed headlamp operation is experiencing an open circuit—meaning there might be a broken wire, faulty connector, or other electrical issue preventing proper communication or operation. It’s important to remember that labeling may vary between different vehicle manufacturers, so the actual code or description could differ slightly depending on the make and model.

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Manufacturer variations for trouble code B1690

Different vehicle manufacturers may use varying codes, descriptions, or labels for similar issues related to autolamp delay circuits. It is essential to verify the specific OEM (Original Equipment Manufacturer) documentation for each vehicle to confirm the exact diagnostic trouble code and its label. Below are some known label variations:

• Volkswagen / Audi: B1690 — « Light delay signal circuit open »
• BMW: 13F0 — « Automatic headlamp delay circuit open »
• Mercedes-Benz: B1690 — « Lighting delay circuit – open »
• Ford: B1690 — « Autolamp delay circuit fault »
• Toyota / Lexus: Code might be labelled as « Lighting delay control circuit open »

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What does trouble code B1690 mean?

In simple terms, ECUs (Electronic Control Units) monitor various circuits to ensure proper functioning of vehicle systems. The B1690 code indicates that the control module has detected an issue within the autolamp delay circuit. This circuit manages the timed operation of headlights when the vehicle switches off or when auto-light functions are activated. The specific trigger is an interruption or open circuit in the wiring, connector, or a malfunction within the associated components.

The code usually appears in the context of corresponding lighting issues, such as headlights not turning on automatically, delayed headlamp shutoff, or warning indicators illuminating on the dashboard. Often, this occurs after a recent electrical repair, battery disconnect, or wiring modification but can also arise from aging wiring or faulty modules.

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Severity and risks of trouble code B1690

The severity of the B1690 code primarily relates to the lighting system, which affects visibility but not the drivability of the vehicle itself. The principal risks include reduced visibility during night driving or adverse weather conditions, which could pose safety issues. Some models may temporarily disable the autolamp function, forcing manual control of headlights until repairs are performed.

In terms of whether the vehicle can be driven, the answer is generally Yes, but with caution. The lighting system’s malfunction does not typically impact the vehicle’s ability to operate, but it is advisable to address the issue promptly for safe nighttime driving.

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Symptoms of trouble code B1690

When the B1690 code is active, drivers may notice key symptoms related to the lighting system’s performance. These symptoms are often minor but important indicators of underlying electrical issues:

• Headlights not activating automatically when entering low-light conditions
• Delayed headlamp turn-off after switching off the ignition
• Warning lights related to lighting control illuminated on the dashboard
• Inconsistent functioning of autolamp features or flickering headlights
• Manual operation still works, but automatic features are compromised

These symptoms highlight that the circuit responsible for timing and control of the headlamps is experiencing issues, often caused by electrical or wiring faults.

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Most likely causes of trouble code B1690

To resolve the B1690 code, technicians should consider the most common causes first. While diagnostics always involve verifying wiring and components, these causes top the likelihood list:

1. Open or broken wiring in the autolamp delay circuit — Damage from corrosion, wear, or accidental disconnection
2. Faulty lighting control module or body control module (BCM) — Malfunction of the electronic component managing lighting functions
3. Corroded or loose connectors — Wiring harness connectors that have become compromised over time
4. Blown fuse or relay related to lighting control — Electrical protection devices that prevent proper circuit operation
5. Sensor malfunction or misreadings — Ambient light sensors or related inputs providing wrong signals

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How to diagnose trouble code B1690

Diagnosing B1690 involves a systematic approach that prioritizes safety and efficiency. Below are generic diagnostic steps applicable across most vehicle brands:

1. Visual inspection: Check the wiring harness, connectors, and fuses related to the autolamp system for obvious damage, corrosion, or loose connections.
2. Verify fuse and relay status: Using the vehicle’s fuse diagram, inspect and test relevant fuses and relays for continuity and proper operation.
3. Check live data signals: Use a scan tool compatible with the vehicle to monitor the lighting control system’s signals and look for anomalies or error codes.
4. Conduct continuity tests: Test wiring continuity from the lighting control module to the headlamps and sensors to ensure no open circuits.
5. Inspect and test components: If accessible, verify the operation of sensors, relays, and the control module itself, possibly replacing faulty units as confirmed by testing.
6. Clear codes and retest: After repairs or inspections, clear the code and perform functional tests to confirm the issue is resolved.

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Possible repairs for trouble code B1690

Addressing the B1690 code involves targeted repairs based on the cause. Recognising whether the issue is a simple wiring fault or a faulty component determines whether a DIY approach or professional intervention is required.

• Replace damaged wiring or repair broken circuits: A basic repair for wiring issues, feasible for skilled DIYers with proper tools.
• Reconnect or replace faulty connectors: Ensuring proper contacts and avoiding corrosion or dirt that causes poor connectivity.
• Replace blown fuse or relay: Usually a straightforward fix, but confirm the correct part number and rating.
• Update or replace the lighting control module or BCM: Requires specialised tools and knowledge; best performed by a professional.
• Replace faulty sensors or related components: Only if diagnostics confirm malfunctioning sensors are the cause.

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Vehicles commonly associated with trouble code B1690 in Europe

While this code can occur across many makes, some brands are more frequently associated with autolamp delay circuit issues based on regional data. These vehicles often feature advanced lighting systems that integrate with other vehicle modules.

Volkswagen / Audi: Common among models with sophisticated lighting control systems, particularly in newer models.

BMW: Found in models with adaptive or automated lighting features, especially in the E and F series.

Mercedes-Benz: Often related to newer models equipped with intelligent light systems.

Ford: Especially in models with automatic headlamp functions and lighting delay features.

Note: Exact affected models may vary, and diagnostics should be tailored to each specific vehicle.

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Frequent mistakes with trouble code B1690

During diagnosis and repair, some common pitfalls can lead to misdiagnosis or ineffective repairs. Awareness of these mistakes improves success rate:

• Assuming the fault is solely in the control module without inspecting wiring: Electrical issues like wiring damage are often overlooked initially.
• Not verifying the integrity of fuses and relays: A blown fuse can mimic more complex circuit faults.
• Ignoring or overlooking connector corrosion or poor contacts: This is a frequent cause of open circuits in lighting systems.
• Replacing components without proper testing: Replacements should always be based on confirmed faults to avoid unnecessary repairs.
• Failing to clear fault codes after repairs: Residual codes may give false impressions of persistent issues.

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FAQ — trouble code B1690

Can this code disappear on its own? Usually, no. Unless the circuit issue is temporary or fixed, the code will persist until diagnosed and repaired.

Can I keep driving? In most cases, yes. The problem affects automatic headlamp functions but does not impact vehicle operation or safety directly. However, driving with impaired lighting can be risky, especially at night.

Why does the code return after clearing it? If the underlying cause (wiring fault, defective sensor, or control module) isn’t addressed, the code is likely to reappear once the system re-tests the circuit and detects the same open condition.